Transmissions of many differing types are well known in the art. Ideally, in a motor vehicle, the transmission should provide stepless adjustment from zero to maximum ground speed, should be easy for the operator to adjust - or even automatic in its performance, should not cause any power loss, and should be low in first cost. Unfortunately, these desired characteristics are not all obtainable and thus no manufacturer can ever introduce the perfect transmission. A continuously variable belt-drive transmission has been used in the past. In one form the effective diameter of one sheave is varied while the other sheave, which is spring loaded to its largest effective diameter position, may have its effective diameter changed by the tension of the belt reacting against the springs. The primary adjustable sheave is typically adjusted by movement of a single side of the sheave. This form of continuously variable belt-drive transmission has the disadvantage in that only a single belt can be utilized in the transmission, which single belt may not be suitable for transmitting the power requirements necessary for many of today's vehicles. U.S. Pat. No. 4,409,862 shows a multi-belt split drive transmission wherein the belts of the drive and driven sheaves of the variable speed portion are both supported by sheave segments, which segments are moved radially inwardly or outwardly by opposed scrolls disposed within the housing that supports the sheave segments, the scrolls in turn being caused to be rotated relative to the housing by a gear train which is interconnected to electrically operated actuators disposed at a location to one side of the transmission. While the design of the above patent overcomes some of the problems and disadvantages of the prior art, this design is relatively expensive due to the utilization of complex gear trains and opposed scrolls.